Making this GPU proof is simple. Make it a primecoin fork with low starting difficulty around 7.0 or less. This will allow everyone with lower end cpus a chance at finding a block before the difficulty gets too high and favors only the overclocked i7's
A primecoin fork will also keep most of the pool operators away.
no it wont.. all it will do is give a botnet operator a very good chance at taking most of the coins.